A horizontal lifeline is typically a steel cable or synthetic rope which is tensioned between two anchor points at either end of an exposed work area. The worker attaches to the lifeline with a lanyard/harness and moves freely between the end anchors. A fall is arrested by the harness, lanyard, horizontal lifeline and ultimately the anchors. Although the forces generated by a fall of this type are easily survivable by the worker, the forces transmitted to the end anchors through the tensioned lifeline can be tremendous. It is thus important, in the event of a fall, to ensure that the end anchors and line itself have not been damaged, and to minimize any subsequent chance for a failure of the system in the event of a further fall.
Synthetic devices which absorb energy, for use in worker protection, are not unique. Personal shock absorbers are conventional, and may be connected directly to a harness worn by a worker. Such shock absorbers are designed to limit the forces experienced by the worker in the event of a fall. Although use of a personal shock absorber will lower the arrest force transmitted to the end anchors of a horizontal lifeline, it is an object of the present invention to provide an improved design of horizontal lifeline system which includes an energy absorber to complement the use of a personal shock absorber by a worker.
Typically energy absorbers have been designed to be permanently installed and withstand harsh environmental conditions. This requires the use of metallic components that are cumbersome and expensive.
References of background interest describing and illustrating personal shock absorbers for workers include U.S. Pat. No. 4,100,996 of Sharp issued Jul. 18, 1978, laid-open Canadian Patent Application Ser. No. 2,109,285 of Wolner et al published May 1, 1994, laid-open Canadian Patent Application Ser. No. 2,103,588 of Crawford published Aug. 7, 1992, and laid-open Canadian Patent Application Ser. No. 2,076,695 of Casebolt published Feb. 25, 1994.
Mechanical shock absorber systems for lifelines are described and illustrated in laid-open Canadian Patent Application Ser. No. 2,116,886 of Duncan published Sep. 10, 1994 and laid-open Canadian Patent Application Ser. No. 2,039,004 of Sulowski et al published Jul. 23, 1992.